<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        var that = null;

        function Preson(uname, age) {
            this.name = uname;
            this.age = age;
        }
        Preson.prototype.setName = function(uname) {
            this.name = uname;
            that = this;
        }
        var p1 = new Preson('tom', 12);
        console.log(p1);
        console.log(that);
        console.log('...');
        p1.setName('bob');
        console.log(p1);
        console.log(that === p1); // true
        console.log(p1.__proto__ === Preson.prototype) // true
        console.log(Function.prototype.prototype); // undefined
    </script>
</body>

</html>